The Ubiquitin Binding Protein TAX1BP1 Mediates Autophagasome Induction and the Metabolic Transition of Activated T Cells.

During immune responses, naive T cells transition from small quiescent cells to rapidly cycling cells. We have found that T cells lacking TAX1BP1 exhibit delays in growth of cell size and cell cycling. TAX1BP1-deficient T cells exited G0 but stalled in S phase, due to both bioenergetic and biosynthetic defects. These defects were due to deficiencies in mTOR complex formation and activation. These mTOR defects in turn resulted from defective autophagy induction. TAX1BP1 binding of LC3 and GABARAP via its LC3-interacting region (LIR), but not its ubiquitin-binding domain, supported T cell proliferation. Supplementation of TAX1BP1-deficient T cells with metabolically active L-cysteine rescued mTOR activation and proliferation but not autophagy. These studies reveal that TAX1BP1 drives a specialized form of autophagy, providing critical amino acids that activate mTOR and enable the metabolic transition of activated T cells.

The ubiquitin modifying enzyme A20 restricts B cell survival and prevents autoimmunity.

A20 is a ubiquitin modifying enzyme that restricts NF-kappaB signals and protects cells against tumor necrosis factor (TNF)-induced programmed cell death. Given recent data linking A20 (TNFAIP3) with human B cell lymphomas and systemic lupus erythematosus (SLE), we have generated mice bearing a floxed allele of Tnfaip3 to interrogate A20's roles in regulating B cell functions. A20-deficient B cells are hyperresponsive to multiple stimuli and display exaggerated NF-kappaB responses to CD40-induced signals. Mice expressing absent or hypomorphic amounts of A20 in B cells possess elevated numbers of germinal center B cells, autoantibodies, and glomerular immunoglobulin deposits. A20-deficient B cells are resistant to Fas-mediated cell death, probably due to increased expression of NF-kappaB-dependent antiapoptotic proteins such as Bcl-x. These findings show that A20 can restrict B cell survival, whereas A20 protects other cells from TNF-induced cell death. Our studies demonstrate how reduced A20 expression predisposes to autoimmunity.

The Increasing Economic Burden with Additional Steps of Pharmacotherapy in Major Depressive Disorder.

OBJECTIVES: Major depressive disorder (MDD) is a common and serious disorder with significant impact on patients and families. The goal of this retrospective cohort study was to determine the economic burden among patients with MDD stratified by number of treatment lines needed for episode resolution. METHODS: Truven Health Analytics MarketScan® claims data were used to identify US patients (≥ 18 years) who were diagnosed with MDD and started on an antidepressant between 2013 and 2017. A generalized linear model estimated direct and employment-related costs for the first 12 months following initiation of treatment across cohorts with increasing number of lines of MDD pharmacotherapy. Analyses were adjusted for demographics and clinical factors. RESULTS: A total of 73,597 patients with MDD comprising the commercial (n = 66,459) and Medicare (n = 7138) populations met selection criteria. Patients who completed treatment for their episode with a single line of antidepressant had the lowest total adjusted direct costs (commercial $9975; Medicare $14,628) followed by those who completed with two lines (commercial $11,723; Medicare $15,526) and those treated with three or more lines of antidepressant regimens (commercial $21,259; Medicare $20,964). Patients who completed treatment with two lines as opposed to one incurred significantly higher direct costs (commercial +$1748, p < 0.0001; Medicare +$898, p = 0.0092). Patients who completed treatment with one line had the lowest employment-related costs compared to other groups. CONCLUSIONS: There was an increased economic burden associated with delay of episode resolution as early as the second line compared to the first line in MDD.

Homeostatic MyD88-dependent signals cause lethal inflamMation in the absence of A20.

Toll-like receptors (TLRs) on host cells are chronically engaged by microbial ligands during homeostatic conditions. These signals do not cause inflammatory immune responses in unperturbed mice, even though they drive innate and adaptive immune responses when combating microbial infections. A20 is a ubiquitin-modifying enzyme that restricts exogenous TLR-induced signals. We show that MyD88-dependent TLR signals drive the spontaneous T cell and myeloid cell activation, cachexia, and premature lethality seen in A20-deficient mice. We have used broad spectrum antibiotics to demonstrate that these constitutive TLR signals are driven by commensal intestinal flora. A20 restricts TLR signals by restricting ubiquitylation of the E3 ligase tumor necrosis factor receptor-associated factor 6. These results reveal both the severe proinflammatory pathophysiology that can arise from homeostatic TLR signals as well as the critical role of A20 in restricting these signals in vivo. In addition, A20 restricts MyD88-independent TLR signals by inhibiting Toll/interleukin 1 receptor domain-containing adaptor inducing interferon (IFN) beta-dependent nuclear factor kappaB signals but not IFN response factor 3 signaling. These findings provide novel insights into how physiological TLR signals are regulated.